Lubricating oil



2352-591 w r A enemies? QQSS Rimmfi Search Patented June 13, 1939 UNITEDTSTATES PATENT OFFICE- LUBRICATING 01L Robert O. Moran, Wenonah, and William H.

James, Paulsboro, N. J., assignors to Socony- Vacuum Oil Company, Incorporated, New York, N. Y,, a corporation ot New York N Drawing.

This invention is directed broadly to the provision of oils for use in automotive engines of modern design, using the newer hard metal bearings, which are in general more susceptible to corrosive agencies under conditionsof use.

Recent changes in automotive engine design, tending toward higher bearing pressures, higher rotative speeds, higher engine temperatures, and the like, have occasioned departure from the use of the usual bearing metals such as babbitt. The newer bearing metals are of difierent nature and, while harder, are in general more susceptible to destructive agencies of a corrosive nature. Typical of these newer bearings are those composed of a cadmium-silver alloy supported upon a steel back, which are now widely installed in certain makes of automobiles. Others of these relatively new bearing metals which may be mentioned are cadmium-nickel and copper-lead alloys, and socalled high lead bearings.

These changes in engine design have been concurrent with marked advances in methods of re fining lubricant oils for automotive use. The demand for oils having lesser changes in viscosity with temperature change; i. e., higher viscosity index (V. I.) has been met by refining lubricants.

intended for motor oils by certain solvent refining or'solvent extraction processes, wherein advantagejs taken of the selective solvent power for hydrocarbons of various types which is possessed/ have enabled supply of an oil of quite desirable' general characteristics, definitely far superior to any oil previously produced from mixed base or asphaltic crudes, and superior to a like, though lesser, degree over oils previously produced from parafdn base crudes.

Application June 5, 1937,

It has been found that the solvent refined motor oils referred to above are for some reason definitely corrosive to the newer bearing metals under normal conditions of automotive use, some. times resulting inbearing failure after only a few thousand miles of normal driving. It is further known that the same reaction, 'viz., corrosion of alloy bearing metals such as cadmiumsilver, also occurs in good paraflinic base oils which have not been subjected to solvent refinl0 ing. The higher the V. I. of the lubricating oil, the more pronounced is the tendency to corrosion of the kind referred to above. Generally speaking, the problem is encountered in oils having a V. I. of 75 or higher, and becomes important in oils having a V. I. of 80 to 85 or higher, and very important in oils of 100 V. I. or higher.

It is an important object of this invention to provide means for satisfactorily..inhibiting or preventing this corrosion from taking place to a serious degree. It is an object of this invention to alter or modify a highly refined motor oil, normally corrosive, by the use of an additive ingredient capable of substantially inhibiting this corrosion. It is an object to provide a substantially non-corrosive motor oil of high V. I. An object of this invention is to provide an additive reagent or ingredient capable of inhibiting the corrosive properties of these oils. The production of solvent refined oils of low corrosive properties under conditions of automotive use is a major object of this invention, as well as the method of production of such oils which couple high viscosity index with low tendency to corrosion.

This invention is based on the discovery that 35 the above objects may be accomplished by the addition to the motor oil of small amounts of aryl amino polysulphides. It is found that when corrosion of the type outlined above on the bearings of the type outlined above occurs, that the corrosion can be inhibited and that the oil can be rendered substantially non-corrosive under conditions far more strenuous than normal driving conditions, by the addition of controlled amounts of these compounds, and particularly disulphide. 1

The reaction products of. aryl amines and eles mentary sulphur are those compounds to which this invention is directed, the preferred member by the addition of controlled amounts of aniline 252. COMPOSlTlON3.

of this group being aniline disulphide. These compounds have the following general formula (NI-IzCsRs) 2S1 where R is a hydrogen atom and/or an alkyl group and S1 may represent 1, 2, 3, or 4 sulphur atoms. The grouping ((Nrncsru) corresponds to aniline or to an alkyl-substituted aniline residue. These compounds are generally prepared by the interaction'of an aniline compound and elementary sulphur. Thus dianiline disulphide can be preparedfrom the interaction of aniline and sulphur after the following scheme:

2 Q as si+nls NE: NH:

' may be removed from the reaction mixture by converting the aniline sulphide products to their hydrochlorides and extraction with hot water. The hydrochloride salt extract then yields the free aniline sulphur complex when neutralized with a base such as sodium hydroxide. The methods of synthesis and purification to form these products are well known in the art of chemical synthesis. The aniline sulphur complex thus obtained consists mainly of a mixture of isomeric aniline disulphides. The crude product as obtained melts at 72-84 0. According to the literature, the isomeric 2,2 diamino diphenyl disulphide melts'at 93 C., the 3,3 isomer melts at 59-60" C., and the 4,4 isomer melts at 81 to 82 C. From the above evidence, it is apparent to those skilled in the art that the product above obtained consists mainly of 'a mixture of the various isomeric forms of diamino diphenyl disulphide, although it is possible that some compounds of other nature are present therein in small amounts. The crude product of the aboveoutlined synthesis melting at 72 to 84 C. .has been. found to be effective ingredient to prevent the corrosive action of motor oils on hard metal bearings when subjected to strenuous use at high temperatures for prolonged times. This material is hereinafter referred to as aniline disulphide.

It is also possible to prepare other compounds having similar eflectiveness when one or more nuclear hydrogens of the aniline member are substituted with alkyls such as methyl or ethyl radicals.

The following sets of data demonstrate the effectiveness of this novel corrosion inhibitor. In all ofthese tests, the oil used was a solvent refined motor oil of S. A. E. 20 rating, having a Saybolt viscosity of 55.3 seconds at 210 F., a fiash point of 435 F. Actual motor operation tests are set forth in Table 1, below. In th tests, a motor oil blank and motor oil blends containing differentproportions of the novel inhibiting ingredient of this invention were subjected to tst in a modified Delco' knock test engin equipped with bearings of cadmium-silver alloy on a steel back. The alloy is about 2.5% silver, a few hundredths of a per cent of copper, and the is tress Search balance of cadmium. The motor was equipped with crankcase oil heaters to maintain oil-temperatures (330 F.) at least equal to those encountered under extreme conditions of automotive use, On each test the test engine was operated for at least 20 hours at a rotative speed the equivalent of an automobile roadspeed of 60 miles per hour. 'In rough terms, each 20 hours of test is the equivalent of exposure of the oil to use in an automobile for 1200 miles of continuous SO-miIe-an-hour driving, a condition far more rigorous than any encountered in normal use. The hearings in the engine were new for each test, and were carefully weighed before and after to determine loss in weight. The neutraliza- Room tion-number (N. N.) of the used oil was measured,

and is recorded as being indicative of the cor;

rosive nature of the oil.

From this it may be seen that theuse of this novel corrosion inhibitor, viz., aniline disulphide, in amounts as small as /4 of 1% prevented corrosion to a substantially complete degree under conditions far more rigorous than any to bemet in practice, while as little as of 1% reduced the hearing loss almost one-half.

An indicative test of considerable merit may be made in the laboratory by suspending a portion of a cadmium-silver alloy bearing in a bath of the oil under test in a glass container, maintaining the oil at about 350 F., and passing air through the oil in contact with the bearing metal. Convenient conditions are as follows: 30 gm. oil,

' 2,000 ml. air per hour, 22 hours. The following table shows results of a series of such tests in which oils containing different proportions of aniline disulphide, and an oil blank were tested, giving the loss in weight of the bearing metal.

The oil used was the same as in Table I:

Table II Loss in weight of heating, mg.

r t I inns and] hide in oil mm 0 n p With indicated Oil secs

From the combined evidence of the exemplary data set forth above, it is evident that the novel inhibiting ingredients herein disclosed, viz.,

' aniline disulphide and alkyl-substituted aniline disulphides are effective agents for the prevention of corrosion under onditions of use of automotive parts, particular y of the newer type alloy nt oisnimisulphide It is preferred to use these ingredients in amounts ranging between 0.25% to 1.0% by weight, although for less-severe service and in oil not highly corrosive in nature, as low as 0.10% may be fully effective for the purposes intended.

That the oils protected by the novel inhibiting agent herein disclosed, viz., aniline disulphide, are also effective to protect copper lead bearings, maybe shown by the following tests wherein an engine test under conditions similar to those outlined in the Delco engine test described above was conducted in a Cooperative Fuel Research engine (commonly known in petroleum and automotive laboratories as a C. F. 3. engine), equipped for the purposes of test with copper lead bearings of the type commonly used in automotive engines of new designs. In these tests, the

oil used was an ofl of the following specifications:

Gravity A. P. I 27.5 Flash 7 F 500 Viscosity Saybo1t at 210 F to Viscosity-index 100 In the following tabulation a comparison is shown between this oil, used alone for 40 'hours, and the same oil to which had been added 0.125%

by weight of aniline disulphide, and exposed to conditions of engine operation for 60 hours.

Table III 7 loss, mg. Neutralization No.

Time engme Ml-H) 1257 Oil-H] opera on on a on a aniline dianiline di- '-1- 'Fi'om the above tabular data it may be noticed that the additive agent is quite efiective in this case, enabling the oil to achieve results at the end of 60 hours operation when protected, that were comparable with the results obtained at the end of 40 hours operation with an unprotected oil.

We claim:

A method of lubricating bearing surfaces which comprises maintaining between the bearing surfaces, one of which contains a characterizing proportion of cadmium, silver, nickel, copper, or lead, a film of lubricating oil which initially produces an effective lubricating action, but would normally tend to corrode the adjacent surface, and maintaining the effectiveness of the lubricating oil by incorporating therein dianiline disulphide in a small but sufllcient proportion to substantially retard the corrosion.

ROBERT C. MORAN.

WILLIAM H. JAMES. 

